This invention relates to a trim system for an outboard motor and more particularly to an improved trim system for a marine outboard drive.
As is well known, it is a common practice to mount marine outboard propulsion systems such as an outboard motor or the outboard drive portion of an inboard/outboard drive on the hull of a watercraft for trim adjustment of the propulsion unit relative to the hull. It has been found that the optimum trim position of the outboard drive, and specifically its propulsion unit relative to the hull, is important in determining the performance of the watercraft. Frequently, the trim is adjusted during operation of the watercraft so as to accommodate the specific running conditions.
Normally, the trim adjustment for a marine outboard drive is provided by a hydraulic trim motor that is interposed between the hull and the outboard drive. By selectively pressurizing the chamber of the fluid motor, it is possible to effect a force between the hull and the outboard drive for moving the outboard drive to the desired trim position. In order to permit trim-down adjustment, the foregoing description being that of a trim-up adjustment, it is normally the practice to depressurize the chamber and permit the propulsion unit to trim down under its own propulsion force.
Although these devices are particularly advantageous, they do have one disadvantage. That is, when the outboard drive is in a relatively fully trimmed down condition, there is a danger that the components of the hydraulic motor can contact each other, cause noise, and cause wear. This is because there is, at best, a mechanical stop that limits the trimmed down position. The stop may be effected be actual engagement between the piston and cylinder of the trim motor. This gives rise to the aforenoted problems.
It is, therefore, a principal object of this invention to provide an improved trim adjustment mechanism for a marine outboard drive.
It is a further object of this invention to provide a trim motor for a marine outboard drive that has an arrangement for providing a stop for limiting or controlling the trimmed down condition without affecting actual mechanical engagement between the components of the trim motor.
It is a further object of this invention to provide a trim motor for trim adjustment of a marine outboard drive wherein a hydraulic lock is established to control the trimmed down position and avoid reduce metal-to-metal contact between the major components of the trim motor.
In order to protect the piston and cylinder from direct engagement, it has been proposed to provide a stop that will limit their degree of relative movement in the trim down condition. However, these stops have been provided externally of the cylinder mechanism and thus have certain possible defects. First, due to misadjustment or operator modification, they may become ineffective and thus the piston and cylinder are subject to wear. In addition, the exposed position of the external stop places it in an area where it can be damaged.
It is, therefore, a still further object to this invention to provide an improved trim down stop mechanism for a hydraulic trim cylinder that is contained internally within the cylinder.